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Sydney Royal Easter Show April 2021 Canon RF 50mm f1.8 STM lens. This lens is very well suited to many uses including street and documentary. It is small, fast and delivers very nice results. In focus parts of the scene are very sharp. In the original I can count eyelashes on the little boy with the Santa Cruz cap and tell the time on the watch of the man with the Beatles T-shirt. At the same time the out of focus parts of the subject are gently rendered with no visual jarring. |
Canon has long included a 50mm f1.8 “nifty fifty” lens in its catalogue. It has traditionally been one of the smallest, lightest and least expensive lenses available for Canon cameras which use the 24x36mm (so-called full frame) sensor or 35mm film as it was in the pre-digital era. Only the EF 40mm f2.8 pancake is smaller.
The Canon Camera Museum Lens Hall lists four FD mount versions from 1976 to 1979, each having 6 elements in 4 groups.
There have been 2 EF mount versions introduced in 1987 and 2015. These also have 6 elements but in 5 groups.
The subject of this post, the RF 50mm f1.8 STM recently became available in Australia and I have been using and testing it over the last week on my EOS R5. This lens also has 6 elements in 5 groups, with one aspheric element in the rear group.
Each of these 50mm f1.8 lenses uses a modified double gauss optical design originally developed in the latter part of the 19thCentury and subsequently used in millions of lenses particularly for the 35mm format.
The original symmetrical design of 1896 has been modified over the years especially in the rear three elements for superior optical properties.
At the time of this review the 50mm f1.8 is the smallest, lightest and least expensive RF mount lens. At the time of writing Adobe Camera Raw does not yet have a profile for the lens.
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This shows the block diagram of the RF 50mm f1.8 alonside the older EF version. You can see they are similar overall but with detail differences including an aspheric element in the newer lens. The EF version locates the optical elements at the rear of the housing. The RF version locates the optics at the front of the housing. Both end up about the same distance from the sensor. |
Who’s it for ?
Any RF mount camera owner who wants a small, light, unobtrusive lens for most kinds of general photography. Actually I have difficulty thinking of a good reason why any RF mount camera owner would not want a nifty fifty tucked away in their camera bag.
As a stand alone lens it makes a very good companion for the photographer out and about seeking photo opportunities without attracting undue attention to him or herself.
Several RF mount lenses are quite large, and therefore obtrusive. The 50mm f1.8 is the opposite. It is unobtrusive.
What’s it for ?
50mm is the classic focal length for a 35mm camera. With judicious use of the two foot zoom the angle of view can be wide enough to take in a scene and narrow enough for environmental portraits without having to get inside your subject’s personal space.
With decently fast AF and very good overall quality the lens is well suited to general photography, family, pets, documentary and street. I would not recommend it for astro. It’s not wide enough and there are some aberrations at the widest apertures.
Which camera body ?
The lens works on any EOS-R body with the RF mount but not on any EF mount body.
The lens has no stabiliser so for best results I recommend the R5 or R6. Of course you can use it on the R or RP but the IBIS on the R5 and R6 does make life easier in low light situations.
Description
Some RF lenses bristle with switches and rings but the 50mm f1.8 looks more like an EF-M lens with minimalist styling and only one switch on the barrel which toggles the function of the single ring from (manual) Focus to Control.
Length with front and rear caps is 66mm
Diameter is 68mm
Mass with filter and both caps is 205 grams.
Filter size is 43mm. All my testing has been done with a B+W XS Pro 007 clear MRC filter mounted.
No lens hood is supplied. There are 2 bayonet lugs near the outer rim of the front of the barrel. Canon lists the ES65B circular bayonet hood for the RF 50mm f1.8. The 78.7mm diameter suggests this is reversible which is desirable.
Some lenses like the RF35mm f1.8 offer a silly little lens hood which screws into the filter ring making it nearly useless if you want a filter in place.
The mount is metal although the main construction material appears to be polycarbonate. There is nothing wrong with this by the way, I have been using polycarbonate lenses for many years with never a single problem involving durability.
Image quality
General observations
The RF 50mm f1.8 delivers very good imaging performance overall. It has enough resolution to express the capabilities of the high pixel count R5.
It does have a few well publicised weaknesses, see below, but in practice these are infrequently relevant to actual photography.
Sharpness, acutance and resolution
In summary:
At f1.8-f2, most of the frame is sharp except the corners which are quite soft with smearing of fine details and color fringing at high contrast edges.
At f2.8, sharpness and contrast improve across the frame including the central area and only the far corners are soft.
At f4 sharpness extends into the corners in a well centered copy.
From f5.6-f11 everything is very sharp across the frame into the far corners with good contrast.
Contrast
Compare to some lenses of more modern design the RF 50mm f1.8 is a bit low on contrast and acutance wide open but this is corrected by closing the aperture about 2 stops to f3.5-f4.
Flare
The lens is quite prone to various types of flare if sun is allowed to fall onto the front element. Flare can be of veiling type or various colored artefacts with the sun or other bright light just in or just out of the frame. I have not bought a lens hood, preferring to keep things simple. I just hold the camera in my right hand and shade the lens with my left hand.
Color fringing
This is mostly seen at the widest apertures with subjects like foliage which can present the lens with high contrast edges.
Bokeh
Out of focus rendition is very important with a lens like this which will often be used for documentary work with out of focus elements in front of and behind the in-focus subject. Overall after several hundred photos in a variety of situations I can say I am pleased with the out of focus rendition. In most shots I have reviewed the out of focus parts of the image are softly rendered delivering a natural looking appearance without any obvious ni-sen, doubling or other nasty looking artefacts.
Distortion
Very slight pincushion can be seen if you go looking for it.
Focussing
I rate single shot AF speed slightly slower than that of the RF 24-105 f4L and significantly faster than the RF35mm f1.8 on the R5 and considerably faster than the EF-M 32mm f1.4 on the EOS-M6.2 with much less chugging back and forth.
Overall AF speed is quick enough that I don’t notice it at all even when shooting fast.
With AF Servo the lens also works well even allowing me to capture birds in flight as long as they are close enough.
As far as I can tell by peering into the front of the lens, it appears that the whole lens assembly moves back and forth when focussing. This would account for the obvious change in effective focal length with focussing. Effective focal length gets longer as the lens moves forward to focus closer. This is often referred to by reviewers as “focus breathing” and is undesirable in video work. It is also undesirable for focus stacking applications.
Compared to some other lenses
The RF 35mm f1.8 uses a more modern design with 11 elements. As a result the 35mm is sharper with more contrast at f1.8-f2.8 right across the frame but especially in the corners. However by f8 the nifty fifty catches up and may even be slightly better at f8-f11.
At f4 the 50mm f1.8 is sharper than the RF 24-105mm f4 L.
My copy of the EF-M 32mm f1.4 is spectacularly sharp right across the frame into the corners straight from f1.4 on the EOS M6.2, and is in fact the sharpest lens I have ever tested at f1.4. However the RF 50mm f1.8 closes the gap as the aperture is reduced and by f8 I actually favour the 50mm f1.8 lens for sharpness and acutance on the R5.
The penalty which the EF-M 32mm lens pays for that optical performance wide open (or rather you the buyer pay) is that it is considerably more expensive, heavier, longer and it focusses slowly with much chugging back and forth.
Out and about
Purists and those who are devoted to photographing test charts will not be wildly enthusiastic about the RF50mm f1.8.
But owners who go forth and take photos with it will be very pleased.
You see the weaknesses of this lens are of little consequence in most photographic situations.
The main “problem” is soft corners at wide apertures.
But ask yourself, in what usage case do you need sharp corners when photographing at f1.8-f2.8 ?
I need sharp corners for landscape when I will be using f8-f16 anyway.
No AF/MF or IS ON/OFF switches
Presumably these switches were left off to keep the price down.
I manage this by making use of the C1, C2, C3 Custom shooting modes.
The only time I want IS off is when I have the lens on a tripod. I have C1 set up for tripod work with IS off in the menu.
I want manual focus when I am making a series of shots to be later stitched into a panorama.
I allocate settings for this to C2 with manual focus set in the menu.
Distribution of sharpness depth
I have recently been investigating how the 3 dimensional distribution of sharpness of my lenses varies with aperture and other parameters such as subject distance and focal length {in zooms). Some lenses perform much better in this respect than others.
I do this by photographing grass and applying the Photoshop [find edges] filter which shows very clearly how sharpness is distributed in the frame. You can read about the method here.
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RF 50mm f1.8 at f11. Nicely even distribution of sharpness here although there is a little more sharpness in front of the focus target than behind it. For landscape work I focus this lens a little higher than the center of the frame. |
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RF 50mm f1.8 at f4. You can see a moustache shaped distribution of sharpness here. Sharpness is well distributed to the edges although there is a little more sharpness in front of the focus target than behind it. |
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RF 50mm f1.8 at f1.8. Sharpness is well distributed front-to-back and side-to-side although there is a little more sharpness in front of the focus target than behind it. |
Conclusion
Although the RF nifty fifty f1.8 is an unpretentious little lens it delivers very good results in a wide range of use cases. It adds very little size or mass to any RF mount body. It is worth serious consideration as the only lens one might mount on the camera for a day out and about with camera.
The R5 with 50mm f1.8 mounted fits nicely in a Think Tank Mirrorless Mover 10 carry bag with two spare batteries, a microfiber cloth and some spare memory cards for a light, compact kit.
The more I use this lens the more I like it. Highly recommended.